1. Field of the Invention
This invention generally relates to a touch system and, more particularly, to a touch system and pointer coordinate detection method therefor.
2. Description of the Related Art
Please refer to FIG. 1, it shows a schematic diagram of a conventional touch system 90. The touch system 90 includes a touch surface 91, cameras 921-924, a plurality of light sources 93 and a processor 94, wherein the touch surface 91 is a reflecting mirror. The cameras 921-924 capture images looking across the touch surface 91 along the touch surface 91. When a user 8 uses his or her finger 81 to approach or to touch the touch surface 91, the cameras respectively capture image windows containing an image of the tip of the finger 81 blocking the light source 93 and a mirror image of finger 81 in the touch surface 91. The processor 94 is coupled to the cameras 921-924 and processes the image windows captured by every camera to determine whether the finger 81 is in contact with the touch surface 91 or not.
Please refer to FIGS. 2a to 2c, they respectively show a schematic diagram of an image window W captured by the cameras 921-924, wherein DA is a dark area in the image window W corresponding to background area and BA is a bright area in the image window W corresponding to the light source 93 or the touch surface 91. When the user does not use his or her finger 81 to approach the touch surface 91, the image window W captured by the cameras 921-924 is like the one shown in FIG. 2a, i.e. the image window W does not contain any pointer information therein. When the user 8 uses his or her finger 81 to approach, but not contact, the touch surface 91, the image window W captured by the cameras 921-924 is like the one shown in FIG. 2b, i.e. the image window W contains an image I81 associated with the finger 81 and an image I81′ associated with the mirror image of finger 81 therein. When the processor 94 identifies that there are bright pixels existing between the images I81 and I81′, the processor 94 identifies that the finger 81 approaches but not in contact with the touch surface 91. When the user uses his or her finger 81 to contact the touch surface 91, the image window W captured by the cameras 921-924 is like the one shown in FIG. 2c, i.e. the images I81 and I81′ in the image window W connect to each other. When the processor 94 identifies that no bright pixel exists between the images I81 and I81′, it identifies that the finger 81 is in contact with the touch surface 91. The detail of identifying whether a pointer is in contact with the touch surface 91 can be found in U.S. Pat. No. 6,947,032.
However, the touch system 90 can only identify whether a pointer is in contact with the touch surface 91 but can not calculate a hovering height of the pointer. Accordingly, the present invention further provides a touch system and pointer coordinate detection method therefor that can identify a hovering height and a plane location of a pointer relative to the touch surface 91 simultaneously.